"It is a potentially legitimate medical shipment. We've seen it at various ports in the nation."

Local news media are now reporting that the shipment of heads was originally sent from the US state of Illinois to Rome, Italy for medical research, then shipped back to Illinois via O'Hare International Airport.

It arrived at O'Hare in mid-December but the shipment was held up because of a paperwork problem.

This morning a suburban crematory came to claim the heads from a local morgue, which had taken custody of the heads.

"Now the cremation service has showed up with the proper paperwork," said a spokeswoman from the Cook County medical examiner's office.

"The medical examiner's office will photograph and X-ray each of the heads" before they are released, she added.